SR20DET Juddering

[gunner93]

Hi all,

I cant recall which thread it was with some suggestions given to solve my misfiring after cold start.

1) I have replace all 4 plugs and it still misfires.

2) I have replace all 4 coils with Splitfire - the juddering reduced but its still there at 2000rpm but stopped after 5 mins of driving.

3)

4)

What should i check next? Thanks.

 

[ichi-go]

Check vacuum lines and cooler hose.

 

[Nicely]

Its possible its the lambda if it goes after warm up... You could try clean your AFM wire too.

 

[tass15]

if it goes away once it comes up to temp, i would look at temp sender unit. the engine runs in open loop mode till the lamda sensor warm up, using the base map on ecu, it will switch to closed loop once sensor is up to temp

 

[gunner93]

Thanks all,

I have done a consult diagnostic today and the AF ratio reads 91% which should have been 100%. Seems like my car is running rich more so at higher RPMs dropping down to 74% which explains why the motor shudders > 2000rpm.

Full medic report here...

http://gunner93.multiply.com/reviews/item/19

Maybe I'll take Nicely's advice to clean the hot wire....

 

[Topper]

Sounds from your write up that our man Nicely got it in one, Geek

 

[sillbeers15]

Its possible its the lambda if it goes after warm up... You could try clean your AFM wire too. - Nicely

Yea,...I love squirting the MINES AFM Cleaner onto the AFM Hotwire...tezzzz.

 

[Topper]

Does brake cleaner do the same job?

 

[Nicely]

Did on mine

 

[gunner93]

I used a cotton swab with some methylated spirit. The hot wire is only about 1.5cm in height but I saw two wires. Is it me or there are actually two hot wires?

 

[ichi-go]

I think you are not supposed to poke it with anything at all. The wire is really fragile. Best thing is to spray it with Contact cleaner. There are some who used brake cleaner and end up killing the afm in ns.com lol

 

[gunner93]

I think you are not supposed to poke it with anything at all. The wire is really fragile. Best thing is to spray it with Contact cleaner. There are some who used brake cleaner and end up killing the afm in ns.com lol

Agree - I was very gentle.

Update : Juddering/misfiring at 2000rpm tp 2500rpm is still there this morning. I had to release to throttle when that happens. I have not gone >4000rpm eversince this problem happened. NOte that the engine idles sweetly and thats a good feeling at the very least. As usual juddering disappears after 5 to 10 minutes when its up to temp.

 

[gunner93]

Sounds from your write up that our man Nicely got it in one, Geek

Tops, Nicely is THE man indeed! :thumbs::nod:

 

[Nicely]

Sometimes...

 

[gunner93]

Update...

Took my S15 for dyno yesterday despite the misfiring. She reads 208 hp on the wheels. (244hp on the fly)... but running abit rich after the mods about 12.5 to 10.6 as the rpm peaks at 6500rpm.

The head tuner guessed it must be my O2 sensor because at part-throttle (close loop) there is this juddering but was ok at full throttle. Furthermore after the car had warmed up after 10 mins of running, the car appears normal.

What do you guys think? Can faulty O2 sensor cause the car to behave like this?

 

[Nicely]

Its possible and not unknown :nod: It will be supplying an incorrect O2 reading, which will affect how it fuels. You can pick up fairly cheap sensors like this one http://www.gendan.co.uk/product_O23WIRE.html. So its worth changing it anyway.

 

[gunner93]

FAQs says the "good sensor should produce an oscillating waveform that flip-flops from near minimum 0.2v to near maximum 0.9v"

The reading from the consult was on mine was 1.2v

Will try to test with a digital oscillascope to re-confirm. Thanks Nicely.

 

[ichi-go]

The manual says:

Idle 0.8 - 1.5V
3,000 rpm 1.4 - 2.0V


It's on EC-98

 

[gunner93]

OH boy! What an unproductive weekend. Went to two workshops, both couldnt came up with anything instead more confusing messages. One guessed it could be the fuel pump, the other suggested me to clean the injectors. Apparently the sensors on my car seem fine. At idle the cars is not misfiring. The juddering only occurs under part throttle load when cold! Once it gets hot, no problem! What does that mean?

 

[gunner93]

Nicely,

Are all Nissan Fuel Filters standard? Do you have the PN for S15 please?

Thanks.